Vacuum apparatus



March 7, 1944. K c HlCKMAN 2,343,665

vAcuuM APPARATUS Filed Feb. 26, 1941 KENNETH c. D.HICK1\L4N INVENTOR BYWL/J M ATTORNEYS Patented Mar. 1944 VACUUM APPARATUS Kenneth C, D.Hickman, Rochester, N. Y., assignor to Distillation Products, Inc.,Rochester,

N. Y., a corporation of Delaware Application February 26, 1941, SerialNo. 380,684

In Great Britain April 5,1940

7 Claims. (Cl. 202205)' This invention relates to'improved high vacuumstills, and particularly self-pumping high vacuum stills. The inventionalso pertains to an improved high vacuum pump.

Although heat losses have heretofore been a real problem in connectionwith high vacuum, and particularly high vacuum unobstructed path stills,the problem has not heretofore been solved. It is, of course, known toregenerate the heat of condensation in ordinary stills but such methodshave not been applicable to high vacuum stills. Also, it has heretoforebeen proposed to utilize the vapors of a molecular still to effect apumping action. However, in this prior art suggestion the heat losseswere the same as in ordinary high vacuum or molecular stills. It was themo tion of distilling molecules rather than the heat contained thereinwhich was slightly used to effect a pumping action. Also it has beenrealized that great heat loss takes place by radiation from the hotvaporizing surface to the cold condensing surface of a high vacuum,unobstructed path still.

This invention has for its object to'provide improved vacuumdistillation apparatus whereby the above dilficulties can be avoided.Another object is to provide high vacuum unobstructed path distillationapparatus in which the heat losses are greatly reduced. Another objectis to provide high vacuum distillation apparatus wherein the hotvaporizing surface and the cool condensing surface are located oppositeto each other but wherein heat losses common to such conditions orconstructions are substantially avoided. A still further object is toprovide an improved selfpumping highvacuum still wherein theheat ofcondensation is utilized to effect evacuation of the still. Anotherobject is to provide improved vacuum pumps. Other objects will appearhereinafter.

These and other objects are accomplished in accordance with my inventionwhich includes high vacuum distillation apparatus wherein the heat ofradiation from the vaporizing plate and/ or the heat of condensation isutilized to vaporize the working fluid in the evacuating ejector orcondensation pump. The invention also includes improved pumps whereinthe pump liquid is very effectively vaporized by passage over a heatedsurface in a thin film by centrifugal force,

In the following examples and description I have given several of thepreferred embodiments of my invention but it is to be understood thatthese are, set forth for purposes of illustration and not in limitationthereof.

In the accompanying drawing is shown a vertical section of a preferredform of my invention, comprising a self pumping high vacuum unobstructedpath still. Referring .to the drawing, numeral 2 designates a gas-tightcasing provided with an integral bell shaped base 4 and a removable bellshaped'top 6. A flange 8 is provided with intermediate gasket In toenable gas tight assembly of 6' with the still casing 2. Numeral l2designates a shaft rigidly housed in bearings l4 and packed gland l6.Numeral l3 designates a circular plate having a depressed cup-shapedportion 20 at the center which is integral with hollow shaft l2. Numeral22 designates acupshaped extension of shaft l2 which is integral withcircular plate 24 and supports and maintains plate 24 rigidly in theposition illustrated. Numeral 26 designates a hollow shaft the axis ofwhich is in line with the axis of hollow shaft l2 and which is integralwith the cup-shaped portion 22 of shaft l2 at breach 60.

Numeral 30 designates a circular plate substantially parallel with plate24 and in spaced relation thereto. Theperipheries of plates 24 and 30are curved downwardly and upper plate 30 has a somewhat greatercurvature so that the two plates cooperate at their peripheries to forman annular nozzle 32. Plate 24 is provided with circular projections 34and 36 as illustrated. Bell shaped top6is provided at its periphery withan integral circular projection 38, and easing 2 is provided with asimilar annular projection 40. Projections 38 and 40 are so formed thatthey will in combination with nozzle 32 form an ejector or condensationpump nozzle. Cooling fluid is circulated through the hollow portions 42and 44 of projections 38 and 40 respectively.

Numeral 46 designates an annular chamber communicating with the exhaustfrom nozzle 32. Numeral 48 designates a conduit connected to the lowerportion of 46 and leading to the hollow shaft l2 to which it isconnected by a packed gland 50. Numeral 52 designates a hole in thecenter of plate 24 and numeral 54 designates a circular baiile integralwith shaft 26. Numeral 56 designates a stationary shaft protruding intoshaft 26. Numeral 60 designates a double or breach opening at the baseof shaft 26. Numeral 62 designates an annular gutter into which circularplate is protrudes. Numeral 64 designates a withdrawal conduit connectedto gutter 62.

Numeral 66 designates a similar annular gutter into which protrudeextension 36 of plate 24. Numeral 68 designates a conduit connected togutter 66. Numeral l0 designates an electrical heating unit forvaporizing plate l8. Numeral J2 designates a conduit connected to a foreor backing pump (not shown).

In operating the apparatus illustrated a partial vacuum is produced inthe system by a pump (not shown) connected to conduit I2. Heatingelement i is putinto operation in order to heat circular vaporizingplate II to distillation temperature. A suitable vaporizable pump fluidis introduced into annual chamber 48 and liquid to be distilled isintroduced into the depressed cup 20 through stationary conduit 58,revolving conduit 26 and breach 0. Shaft I2 is then rotated by means offorce applied to pulley 14. As a result, vaporizing plate ll and plates24 and 30 rotate as one integral unit. Liquid to be distilled flowsdownward through conduit 28 and breach ill into cup 20 and is thencaused to flow by centrifugal force over the top of vaporizing surfaceII in the form of thin film. During the passage thereover distillationtakes place. Undistilled residue is thrown into annular gutter 62 and iswithdrawn from the still through conduit i4. Vapors generated duringdistillation pass directly to condensing surface 24 where they arecondensed and thrown by centrifugal force to projection 28 and then intogutter 64 from which the condensate is withdrawn through conduit '8.

During the foregoing operations the pump fluid in 46 flows by gravitythrough conduit 44 upwardly through the center of shaft I 2 into bell22. It is then lifted by centrifugal force past the baiile 54 andthrough the circular opening 52. It then flows as a thin film over thetop surface of plate 24, or in other words over that side of plate 24away from plate ll. During passage it is heated primarily by radiationfrom plate 24 and also by the vapors condensing on the opposite side ofplate 24. This heat is taken up by the pump fluid which is vaporized andthe vapors thus generated flow by a combination of centrifugal force andtheir own kinetic energy through annular nozzle 22, as a jet or streamof high velocity. Gases present in the still pass into this jet streamthrough openings 18 and II and become entrained in the vapor jet and arethus forced into chamber 46. The vapors from the jet are condensed bycontact with the cool walls of chamber 48 which are cooled by coolingfluid circulated through 42 and 44. Permanent or uncondensed gases arewithdrawn through conduit 12 by the backing pump (not shown). Inpractice the still will become a little hotter than normal during thestarting period and the extra radiant heat will start the pump inaction, distillation will then commence and the still will cool down toits steady running temperature.

Any pumping fluid which is not vaporized on the top of plate 24 isthrown by projection 34 against the bottom of plate 30 so that thestream issuing from nozzle 32 is a relatively homogenous vapor.

The combination illustrated provides an annular or circular jet nozzlewith two annular intakes thereto. The intakes are of high admittance andaccordingly a condensation pump of high capacity is located in the stilljust where it is needed, namely, as near the place from which v the gasis to be removed as is possible.

The rate of flow of the pump fluid to the plate 24 can be controlled bya valve such as shown at II. It will be realized that the rate ofintroduction of pump fluid onto plate 24 will be adjusted to suit thetemperature of the vaporizing surface and the rate of distillationthereon. If

the rate of distillation and the temperature are low, the pump fluidshould be introduced at a correspondingly low rate since if it isintroduced in too great an amount, it will effectively cool condensingsurface 24 but it will not be eiIectively vaporized by the heat ofradiation and/or condensation.

The pump fluid utilized should have a boiling point which is somewhatlower under the conditions prevailing than the boiling point of thedistillate to be produced in the still at the time the pump fluid is tobe used. The procedure is of greatest value for the distillation ofsubstances at high temperatures such as above 200 C. A satisfactory pumpfluid for such conditions would be dipropylphthalate. The pump fluidshould be one which enables a satisfactory low condenser temperature tobe used but which will be substantially vaporized at said condensertemperature. However, it is not necessary to utilize a condenser whichis at room temperature. With many substances it is satisfactory andindeed preferred to utilize a condenser temperature of or perhaps even150 C. or higher. If the use of high condenser temperatures is asatisfactory method of operation in connection with the substance to bedistilled, a higher boiling point pump fluid can be used, and hencegreater pumping eillciency will result. The following are examples ofpump fluids and condenser temperatures which may be used.

Condenser temperature near- 100, diethyl phthalate dipropyl phthalatedibutyl phthalate diamyl phthalate l80-200, dioctyl phthalate or dioctylsebacate In place of these pump fluids the methyl and ethyl esters ofthe fatty acids can be used. Free fatty acids such as oleic stearic andnatural mixtures of free fatty acids can be used.

Many modifications can be made in the above described apparatus withoutdeparting from the spirit or scope of my invention. For instance, the

condenser plates 24 and 30 need not be fastened to the same shaft asvaporizing plate i8. They can be rotated by a separate shaft. Alsorotation of either or both of plates 24 and 30 is unnecessary althoughadvantageous. If desired they can be stationary but shaped so that theyhave a slight slope, in which case the pump fluid would pass over thesurface by gravity.

Although the invention is of particular value in connection withcentrifugal stills because they have a high rate of distillation andaccordingly a high heat of condensation, the invention can be utilizedwith advantage in connection with ordinary gravity flow stills. The pumpfluid passing through conduit 48 can be caused to flow by means of apump instead of by gravity, if desired.

The invention has the particular advantage that the extravagantexpenditure of heat associated with high vacuum unobstructed path, highvacuum short path, or molecular distillation need no longer be wasted Afurther and important advantage is that the condensing surface ismaintained at a definite temperature throughout the distillation; i. e.,the temperature at which the pump fluid vaporizes. This is important inconnection with the distillation of substances containing solid mattersuch as sterols since they are thus prevented from crystallizing anddepositing on the vaporizing surface. Also, an important advantage isneeded, namely immediately at the vaporizing surface,

' thus entrain and that the pumping is produced right in the still andright at the place where it is or near the vaporizing zone. The stilland pumping construction is also simplified so that a complete still canbe directly fastened to the primary vacuum lines which are able toprovide a cheap and efficient form of vacuum. v

The rate of rotation is not of critical importance and in general willbe between 200 and 30,000 R. P. M. per minute. Rates of 500 to,4,000

R. P. M. are usually convenient. For further de-' tails regarding theconstruction and operation of rotating stills reference is made to my U.S. Patents 2,210,927 and 2,210,928.

What I claim is:

1. Vacuum distillation apparatus comprising inv combination a vaporizingsurface, a condensing surface, means for introducing .distilland ontomeans for removing undistilled residue from the vaporizing surface,

1 the vaporizing surface, means means for removing distillate from thecondenspump means for bringing the the evacuating jet pump the ingsurface, a jet working fluid of intake side of which communicates withthe still vaporizing and conand the space between the densing surfacesinto thermal contact with the distilling vapors, whereby duringoperation of the still the heat from the vapors passes to the workingfluid causing the working fluid to be converted into vapors which passthrough the jet pump and thus entrain and remove gases from the still.

2 Vacuum distillation apparatus comprising in combination a vaporizingsurface, a condensin surface separated from the vaporizing surface bysubstantially unobstructed space, means for introducing distilland ontothe vaporizing surface, means for removing undistilled residue from thevaporizing surface, means for removing distillate from the condensingsurface, an evacuating jet pump, means for exposing the working fluid ofthe evacuating jet the intake side of which communicates with the stilland the space between the vaporizing and condensing surfaces, to theradiation of the vaporizing surface and the heat content of thedistilling vapors whereby during operation of the still the heat fromthe vapors and heat of radiation pass to the working fluid causing theworking fluid to be converted into vapors which pass through the jetpump and remove gases from the still.

.3. Vacuum distillation apparatus comprising in combination a vaporizingsurface, a condensing surface located opposite to the vaporizing surfaceand separated therefrom by substantially unobstructed space, means forintroducing distilland onto the vaporizing surface, means for removingundistilled residue from the vaporizing surface, means for removingdistillate from condensing surface an evacuating jet pump the intakeside of which communicates with the system and the space between thevaporizing and condensing surfaces, the throat of said jet pumpcommunieating with the sideof the condensing surface away from thevaporizing surface and, means for introducing evacuating or pump workingfluid onto that side of the. condensing surface which is farthest fromthe vaporizing surface, whereby during operation of the still the heatof radiation from the vaporizing surface and the heat from the vaporscondensing on one side of the conother side of the working fluid todensing surface pass to the working fluid on the pass through the jetpump pass through the jet pump thus causing ,evacuation of the still.

4. Vacuum distillation apparatus comprising in combination a vaporizingsurface, a condensing surface, means for introducing distilland onto forremoving undistilled residue from the vaporizing surface; means forremoving distillate from the condensing surface an evacuating jet pumpmeans for bringing together the heat radiated from the vaporizingsurface and the working fluid of the evacuating jet pump the intake sideof which communicates with a systemto be evacuated, whereby duringoperation of the still the heat radiated from the vaporizing surfacecauses the working fluid to be converted into vapors which and thusentrain and remove gases from the system.

5. High vacuum unobstructed path distillation apparatus comprising incombination within a closed system, a rotatable vaporizing surface, acondensing surface separated from the vaporizing surface bysubstantially unobstructed space, means for introducing distilland ontothe approximate center of the vaporizing surface, means means forintroducing a condensation pump working fluid onto that side of thecondensing surface away from for conveying condensation pump workingfluid vapors from that side of the condensing surface away from thevaporizing surface to the throat of the jet pump and passages for gasesin the system to flow to the intake side of the jet pump whereby duringoperation of the still distilland is caused to flow in a thin film bycentrifugal force over the rotating vaporizing surface, distillingvapors are condensed and up their heat to the pump fluid on the oppositeside of the condensing surface which is also heated by radiation fromthe vaporizing surface and thus the pump fluid is vaporized and passesthrough the jet pump and entrains gases within the system.

6. High vacuum unobstructed path distillation apparatus comprising incombination within a closed system, a rotatable vaporizing surface, arotatable condensing surface separated from the vaporizing surface bysubstantially unobstructed space, means for introducing approximatecenter of the vaporizing surface,

means for removing undistilled residue from the vaporizing surface,means for removing distillate from the condensing surface, means forintroducing a condensation pump working fluid onto the approximatecenter of that side of the condensing surface away from the vaporizingsurface an evacuating jet pump. ing condensation pump working fluidvapors from that side of the condensing surface away from the vaporizingsurface to the throat of the jet pump and passages for the gases in thesystem to flow to the intake side of the jet pump whereby duringoperation of the still, distilling vapors are condensed on thecondensing surface and simultaneously give up their heat. to the pumpfluid on the opposite side of the condensing surface which is alsoheated by radiation from the vaporizing surface and thus the pump fluidis vaporized and passes through .the jet pump causing evacuation of thestill.

'7 A condensation or ejector pump adapted to evacuate a closedreceptacle and comprising in the vaporizing surface means simultaneouslygive distilland onto the means for conveycombination a rotatablevapor-producing means which is rotatable about an axis so that pumpfluid applied near to-the axis of rotation is caused to flow in a thinmm by centrifugal force radially with respect to the axis, means forheating the vapor-producing means, means for introducing pump fluid ontothe vapor-producing means at a point near to the axis of rotation. meansfor collecting unvaporlzed pump fluid at the periphery oi the rotatablevapor-producing means, a nomle adapted during operation to form a jet ofvapors which nozzle is so connected to to the vapor-producing means thatthe vapors 10 returning at least part or the condensed vapors to therotatable vapor-producing means.

KENNETH C. D. HICKHAN.

